I read the essay that the Church released on LDS.org entitled "Plural Marriage and Polygamy in Kirtland and Nauvoo."

In the essay, the church admits that Joseph Smith had 30-40 wives, including one 14 year old. The average marrying age for that portion of the US at that time was 22 years old for girls (women). To read the 14 year old account's, Helen Mar Kimball's, account of her "marriage" is heartbreaking.